Process for Controlling Indium Clustering in InGaN LEDs Using Strain Arrays

ABSTRACT

Exemplary embodiments provide MQW semiconductor devices and methods for their manufacture. The MQW semiconductor devices can be formed by growing a MQW active region over a nanoscale periodic strain array. By using the nanoscale periodic strain array, the position, size, and composition of the In-rich clusters in the MQW active region can be controlled. This control of In-rich clusters can result in tighter wavelength control, which can be important for applications, such as, for example, lasers and LEDs.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/735,199, filed Nov. 10, 2005, which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to light emitting devices, and, moreparticularly, to light emitting devices with multiple quantum wells(MQW).

BACKGROUND OF THE INVENTION

Commercial lighting and personal electronics such as cellular phones arefueling the rapid market growth in the LED (light emitting diode) andlaser industry. Companies are now faced with the challenge of creatingmore effective manufacturing techniques that have a tighter control ofproperties and yield better quality devices.

It is known that the luminescent efficiency of visible and near-UVwavelength InGaN/GaN LEDs depends on the distribution of Indium (In)within the LED active region, which includes multiple quantum wells(MQW) and/or quantum dots. Conventional manufacturing processes,however, have poor control over the amount of In-clustering that takesplace and the uniformity of the In-clusters in the MQW active region

Thus, there is a need to overcome these and other problems of the priorart and to provide light emitting devices and methods for theirmanufacturing having better control of the In-clustering process.

SUMMARY OF THE INVENTION

According to various embodiments, the present teachings include asemiconductor device. In the semiconductor device, a first doped layerhaving a first conductivity type is disposed over a semiconductorsubstrate. A multiple quantum well (MQW) structure is then formed overthe first doped layer and followed by a second doped layer formed overthe MQW structure. The second doped layer has a second conductivity typeopposite to the first conductivity type. A third doped layer having thesecond conductivity type is then formed over the second doped layer. Inthe semiconductor device, a nanoscale strain array is disposed within atleast one of the first doped layer, the second doped layer and the thirddoped layer.

According to various embodiments, the present teachings also include amethod for making a semiconductor device. In the method, a first dopedlayer having a first conductivity type is formed over a semiconductorsubstrate. A nanoscale strain array having the first conductivity typeis then disposed within the first doped layer, over which a multiplequantum well (MQW) structure is formed. A second doped layer having asecond conductivity type is then formed over the MQW structure andfollowed by a third doped layer having a second conductivity type formedover the second doped layer.

According to various embodiments, the present teachings also include asemiconductor laser device. The semiconductor laser device includes alaser cavity, and a laser active structure, that is disposed within thelaser cavity. The laser active structure includes the semiconductordevice of claim 1.

According to various embodiments, the present teachings further includea semiconductor device. In this device, an n-type GaN layer is stackedover a semiconductor substrate. A nanoscale heteroepitaxy (NHE) bufferlayer is disposed between the n-type GaN layer and the semiconductorsubstrate. A nanoscale strain array including at least one of GaN orAlGaN is disposed within the n-type GaN layer. The strain arraygenerates a periodic strain field. A multiple quantum well (MQW)structure including at least one of InGaN or AlInGaN is formed over then-type GaN layer and overlapped with the periodic strain field. Thedevice also includes a p-type AlGaN layer stacked over the MQW structureand a p-type GaN layer stacked over the p-type AlGaN layer.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 depicts an exemplary MQW semiconductor device for LEDs inaccordance with the present teachings.

FIGS. 2A-2C depict an exemplary process for forming the NHE buffer layerand the first doped layer for the MQW semiconductor device in accordancewith the present teachings.

FIG. 3 depicts an alternative exemplary MQW semiconductor device inaccordance with the present teachings.

FIG. 4 depicts an additional exemplary MQW semiconductor device inaccordance with the present teachings.

FIG. 5 depicts an exemplary semiconductor laser device in accordancewith the present teachings.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of theinvention, an example of which is illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In thefollowing description, reference is made to the accompanying drawingsthat form a part thereof, and in which is shown by way of illustrationspecific exemplary embodiments in which the invention may be practiced.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the invention and it is to be understoodthat other embodiments may be utilized and that changes may be madewithout departing from the scope of the invention. The followingdescription is, therefore, merely exemplary.

While the invention has been illustrated with respect to one or moreimplementations, alterations and/or modifications can be made to theillustrated examples without departing from the spirit and scope of theappended claims. In addition, while a particular feature of theinvention may have been disclosed with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular function. Furthermore, to the extent thatthe terms “including”, “includes”, “having”, “has”, “with”, or variantsthereof are used in either the detailed description and the claims, suchterms are intended to be inclusive in a manner similar to the term“comprising.” The term “at least one of” is used to mean one or more ofthe listed items can be selected.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein. For example, a range of “less than 10” can include any and allsub-ranges between (and including) the minimum value of zero and themaximum value of 10, that is, any and all sub-ranges having a minimumvalue of equal to or greater than zero and a maximum value of equal toor less than 10, e.g., 1 to 5.

FIGS. 1-5 depict exemplary embodiments of MQW semiconductor devices forthe applications of, for example, LEDs and lasers, and methods for theirmanufacture. The MQW semiconductor devices can be formed by growing aMQW active region over a nanoscale periodic strain array. By using thenanoscale periodic strain array, the position, size, and composition ofthe In-rich clusters in the MQW active region can be controlled. Thiscontrol of In-rich clusters can result in tighter wavelength control,which can be important for LED applications, such as, for example, colormixing.

The disclosed MQW semiconductor device can include nanoscale strainarrays and MQW active regions formed over a substrate. As used herein,the term “nanoscale strain array” refers to a nanostructuredhetero-interface placed in the vicinity of the MQW active region. Thenanoscale strain array can generate a periodic-strain-field in the firstquantum well. The periodic-strain-field can then be propagated intosubsequent quantum wells. Accordingly, once the distribution of In-richclusters is controlled in the first quantum well, this control will bereplicated in subsequent quantum wells, for example, with a similarspatial layout, leading to a stack of spatially organized In-richclusters in the MQW active region. In this manner, the nanoscaleperiodic strain arrays can be used to control and/or optimize theformation, the position, and/or size of In-rich clusters within the MQWstructure.

In various embodiments, the nanoscale strain arrays can be formed by,for example, one or more of interferometric lithography (IL) and/ornanoimprint lithography (NL), with periodic structures having nanoscaledimensions of, for example, about 10-100 nm. And as an additionalexample, the nanoscale dimensions of the periodic structures can be lessthan about 20 nm.

As used herein, the term “interferometric lithography” (IL) refers to alithographic process that involves interference patterns of two (ormore) mutually coherent light waves. The angles between the lightpropagation vectors of the waves are sufficiently large to produce aninterference pattern that has a high spatial frequency.

As used herein, “nanoimprint lithography” refers to a lithographicprocess that involves a stamp having embossed nanostructures. The stampcan be pressed onto, for example, a resist material at high temperatureand then released from the resist material when it is cooled to a lowtemperature. Thus, the exemplary resist material can be imprinted withthe negative patterns of nanostructures of the stamp.

IL and/or NL can produce nanostructures or patterns of nanostructuresover wide, macroscopic areas at low cost in comparison to othertechniques such as electron beam lithography. In addition, IL or NL canbe used to generate arrays of nanostructures (e.g., protrusions orchannels) whose dimensions vary semi-continuously in the plane of thesurface of the material being patterned. Accordingly, the IL or NLgenerated arrays of nanostructures can be used as nanoscale periodicstrain arrays for the disclosed MQW semiconductor devices.

The MQW semiconductor devices can be formed using a variety of crystalgrowth techniques including, but not limited to, metal-organic chemicalvapor deposition (MOCVD), molecular-beam epitaxy (MBE), gas source MBE(GSMBE), metal-organic MBE (MOMBE), atomic layer epitaxy (ALE), ororganometallic vapor phase epitaxy (OMVPE). Accordingly, variousepitaxial films (i.e., epilayers) can be formed over the substrate ofthe MQW semiconductor devices.

In various embodiments, nanoscale heteroepitaxy (NHE) techniques can beused to fabricate MQW semiconductor devices. As used herein, the term“NHE” refers to a technique for the growth of thin films in a mannerwhich localizes and apportions strain at the substrate-epilayerinterface, and enables strain to decay significantly with increasingepilayer thickness after the epitaxial film growth. Thus, the NHEtechniques can be used for lattice-mismatched heteroepitaxy growth, suchas, for example, lateral epitaxial overgrowth, pendeo-epitaxy andcantilever-epitaxy. In addition, the NHE techniques can provide ahomogenous defect reduction across the entire wafer, for example,allowing regular, unrestricted processing on these wafers and the fullcost benefits of scaleability.

In various embodiments, the MQW semiconductor devices can be formedusing a III-V compound semiconductor materials system. In thesematerials systems, examples of the group III element can include Ga, Inor Al, which can be formed from exemplary respective group IIIprecursors, such as trimethylgallium (TMGa) or triethylgallium (TEGa),trimethylindium (TMIn) or trimethylaluminum (TMAl). In the III-Vmaterials system, examples of the group V element can include As, Sb, N,or P. Exemplary group V precursors, such as ammonia,tertiarybutylphoshine (TBP), or arsine (AsH3) can be used to provideaccording exemplary element such as N, P or As. In various otherembodiments, many different III-V semiconductor alloy compositions canbe used, based on the known relationships between bandgap energy andlattice constant of different III-V compounds.

In the following description, III-V semiconductor alloy compositions canbe described by the combination of III-V elements, such as, for example,InGaN, GaN, AlGaN, AlInGaN, InGaAs, AlGaInAs, GaNAs, InGaAsP, orGaInNAs. Generally, the elements in a composition can be combined withvarious molar fractions. For example, the semiconductor alloycomposition InGaN can stand for In_((x))Ga_((1-X))N, where the molarfraction, x, can be any number less than 1.00. In addition, depending onthe molar fraction value, various semiconductor devices can be made bysimilar compositions. For example, an In_(0.3)Ga_(0.7)N (where x isabout 0.3) can be used in the MQW active region of LEDs for a blueemission, while an In_(0.43)Ga_(0.57)N (where x is about 0.43) can beused in the MQW active region of LEDs for a green emission.

FIG. 1 depicts an exemplary MQW semiconductor device 100 used, forexample, for LEDs. The device 100 can include stacked layers including asubstrate 110, a buffer layer 120, a first doped layer 130, a strainarray 140, a MQW structure 150, a second doped layer 160, and a thirddoped layer 170. It should be readily obvious to one of ordinary skillin the art that the device 100 depicted in FIG. 1 represents ageneralized schematic illustration and that other layers may be added orexisting layers may be removed or modified.

The substrate 110 can be a semiconductor substrate formed of, forexample, silicon, sapphire, or silicon carbide. In various embodiments,a silicon-on-insulator (SOI) can be used for the substrate 110. Thebuffer layer 120 can be formed over the substrate 110. The buffer layer120 can be a NHE buffer layer, which can act as a compliant layerbetween the substrate 110 and the subsequent first doped layer 130.

FIG. 2A-2C depicts an exemplary process for forming the NHE buffer layer120 and the first doped layer 130. As shown in FIG. 2A, the NHE bufferlayer 120 can include nanopatterned structures 125 interspersed by aselective growth mask 126 on the substrate 110. The nanopatternedstructure 125 can be formed in the areas defined by the selective growthmask 126. The selective growth mask 126 can be, for example, a siliconnitride (SiN_(x)) mask. In various embodiments, the nanopatternedstructure 125 can be, for example, self-assembled nanoscale pattern ornanotemplates formed by IL or NL.

Nanoscale facetted crystal pyramids 128 can then be formed from thenanopatterned structures 125 by NHE growth defined by the selectivegrowth mask 126. In various embodiments, the nanopatterned structures125 and the nanoscale facetted crystal pyramids 128 can be formed usingsame materials such as the III-V materials, for example, GaN. In anexemplary embodiment, a planar crystal layer such as a GaN layer can beinserted between the substrate 110 and the NHE buffer layer 120.

In FIG. 2B, the facetted crystal pyramids 128 can be nucleation sitesfor the subsequent epi growth. For example, the crystal pyramids 128 canbe coalesced (depicted as 129) and then form the first doped layer 130(shown in FIG. 2C and FIG. 1). The NHE process can allow a 3-dimentionalstrain relief, which allows the facetted crystal pyramids 128 to growlaterally as well as vertically to accommodate the largelattice-mismatch strain.

The first doped layer 130 can be a layer with a thickness of, forexample, about 50 nm to 500 nm. The first doped layer 130 can be formedof, for example, GaN, which can be made an n-type epilayer by dopingwith various impurities such as silicon, germanium, selenium, sulfur andtellurium. In various embodiments, the first doped layer 130 can be madea p-type layer by introducing beryllium, strontium, barium, zinc, ormagnesium. Other dopants known to one of ordinary skill in the art canbe used.

Referring back to FIG. 1, the strain array 140 can be formed in thefirst doped epilayer 130. The strain array 140 can be formed of, forexample, GaN and/or AlGaN. The strain array 140 can be further dopedwith an n-type or p-type conductivity similar to the first doped layer130. In some embodiments, the strain array 140 can be a square array of100 nm steps and 100 nm spaces (a period of 200 nm). In otherembodiments, the strain array 140 can have a variety of other nanoscaledpatterns, such as, for example, hexagonal lattice symmetry.

The strain array 140 can be formed by, for example, IL techniques withexemplary nanoscales of, for example, about 67 nm pitch. Suitablewavelengths for the IL process include, but are not limited to: I-line(364 nm Ar-ion laser and 355 nm tripled YAG laser); 244 nm (doubledAr-ion); and 213/193 (fifth harmonic YAG/ArF laser for exposure in air,the minimum pitches can be, for example, about 182, 177, 122, and 107/97nm.

The strain array 140 can also be formed using immersion IL techniques,which can extend the minimum available pitch to about 74/67 nm. Thestrain array 140 can further be formed using nonlinear processes, whichcan extend the available pitch to about 34 nm or less, and as anadditional example, less than about 20 nm. Specifically, the nonlinearprocesses can be used in photoresist exposure and development processes,as well as in subsequent pattern transfer steps of the IL process. Inaddition, the nonlinear IL process can decrease threading defects andincrease the density of In-rich clusters to, for example, a density of10¹¹ cm⁻² or higher. In various embodiments, the strain array 140 canalso be formed by combining IL with NL or electron beam patterning.

In various embodiments, because of the large-area nanoscale capability,the IL techniques can be readily extended to manufacturing requirementsincluding automatic wafer handling and extension to larger size wafersfor establishing efficacy of photonic crystals for light extractionfrom, for example, visible and near-UV LEDs.

As shown in FIG. 1, the MQW structure 150 can be formed over the firstdoped layer 130 and overlapped with the strain field generated by thestrain array 140. The MQW structure 150 can be formed of, for example,alternating layers of InGaN and GaN or two InGaN layers having differentcompositions. In various embodiments, the MQW structure 150 can beformed of alternating layers of AlInGaN and AlGaN or two AlInGaN layershaving different compositions. While not intending to be bound by anytheory, it is believed that the local increase in system free energycaused by the strain array 140 during formation of the MQW structure 150relaxes the kinetic barrier to atomic diffusion of indium (In). Theperiodic strain field caused by the strain array 140 can penetrate atleast one of the quantum wells of the MQW structure 150 to forceIn-clustering in a uniform array and to over-ride the self assembledIn-clustering process. Once In-rich clusters form in the first quantumwell, the strain field can be automatically transferred into subsequentquantum wells to replicate and/or propagate the spatial layout ofIn-rich clusters from the first quantum well, to the subsequent quantumwell, and so on. As a result, ordered arrays of In-rich clusters can beformed.

It is believed that the stress and strain associated with the strainarray 140 falls exponentially in the MQW growth direction and the extentof the exponential decrease can be similar to the period of the strainarray pattern. For example, in a strain array with a 200 nm period, thestrain associated with the pattern can extend about 200 nm in the MQWgrowth direction.

In various embodiments, because the strain field generated by the strainarray 140 can be highly periodic, the position, size, and composition ofthe In-rich clusters can be controlled. For example, for spatial controlof In-clusters, the strain field period of the strain array 140 can becontrolled to be similar to the average self-assembledin-cluster-period. The In-rich clusters can be, for example, in a rangeof about 5-50 nm in size, and as an additional example, in the range ofabout 5-10 nm. The area density of the In-rich clusters can be 10¹⁰ cm⁻²or more. Therefore, the high-periodicity of IL or NL pattern arrays forthe strain array 140 can improve the uniformity of In-clustering, whichcan lead to a more reproducible and higher-yield device process withtighter control of, for example, LED wavelength as required for colormixing.

Referring back to FIG. 1, the second doped layer 160 can also beincluded in the MQW semiconductor device 100 and formed over the MQWstructure 150. The second doped layer 160 can be a layer with sufficientthickness to keep indium clusters within the MQW structure 150. Thethickness of the layer 160 can be, for example, about 500 to about 2000nm. The second doped layer 160 can be formed of, for example, AlGaN. Thesecond doped layer 160 can be doped with a conductivity type similar tothe third doped layer 170.

The third doped layer 170 can be formed over the second layer 160 to capthe MQW semiconductor device 100. The third doped layer 170 can beformed of, for example, GaN and doped to be an n-type or p-type. Invarious embodiments, if the first doped layer 130 is an n-type layer,the layer 160 and/or 170 can be a p-type layer and vice versa. The thirddoped layer 170 can have a thickness of about 50-500 nm.

In various embodiments, ordered In-clusters in the MQW active region anbe achieved by correctly placing the strain array 140 in the vicinity ofthe MQW structures 150, for example, as shown in FIG. 1. In anotherexemplary embodiment, the strain array can be disposed on an oppositeside of the MQW structure. FIG. 3 depicts an alternative exemplary MQWsemiconductor device 300, in which the strain array 340 is disposedwithin the second doped layer 160, as opposed to being disposed withinthe first doped layer 130 in the MQW semiconductor device 100. However,one of ordinary skill will recognize that the strain array can also bedisposed within the third doped layer 170. In this case, post-growthannealing would probably be required to allow the strain array to exertits influence and re-organize the In-clustering in the MQW region belowit.

In various embodiments, electrodes and/or electrical contacts can beadded to the MQW semiconductor devices. FIG. 4 depicts an additionalexemplary MQW semiconductor device 400. It should be readily obvious toone of ordinary skill in the art that the device 400 depicted in FIG. 4represents a generalized schematic illustration and that otherlayers/dopants may be added or existing layers/dopants may be removed ormodified.

As shown in FIG. 4, the MQW semiconductor device 400 can includeconductive structures/layers formed over an etched exemplary MQW layeredstructure 405. The structure 405 can be similar to the structure of thesemiconductor device 100 or the semiconductor device 300. Specifically,the etched layered structure 405 can include a substrate 410, an NHEbuffer layer 420, an n-type layer 430, a strain array 440, a MQWstructure 450, an n-type barrier layer 460, and a p-type layer 470. Eachlayer can be epitaxially grown on the layer below in sequential fashionas described above. In various embodiments, the semiconductor device 400can invert the vertical positions of the p-type and n-type layers.

As illustrated in FIG. 4, the conductive structures of the MQWsemiconductor device 400 can include n electrodes 480, a transparent pelectrode 490, and a p-bond pad 495 fabricated on surfaces of the etchedlayered structure 405. Each of conductive structures can be formed fromtitanium (Ti), aluminum (Al), platinum (Pt), nickel (Ni) or gold (Au) ina number of multi-layered combinations such as Al/Ti/Pt/Au, Ni/Au,Ti/Al, Ti/Au, Ti/Al/Ti/Au, Ti/Al/Au, Al or Au. In various embodiments,the n electrodes 480 and the p-bond pad 495 can be used as ohmiccontacts.

The n electrodes 480 can be formed on surface of the n layer 430 byfirst etching the layered structure 405 and forming mesa structures 485using standard ICP (i.e., inductively coupled plasma) mesa etchtechniques known to one of ordinary skill in the art. The n electrodes480 can then be patterned on the surface of the etched n layer 430(i.e., the mesa structures 485) by metallization processes, for example,metal evaporation or deposition. In various embodiments, the nelectrodes 480 can be annealed after the metallization process at a hightemperature, for example, about 700-800° C. The n electrodes 480 can beformed of, for example, a layered metal combination, such asAl/Ti/Pt/Au.

The p electrode 490 can be a transparent layer formed on a surface ofthe etched layered structure 405, more particularly, on the surface ofthe p layer 470. The p bond pad 495 can then be patterned on top of thetransparent p electrode 490. In various embodiments, metallizationprocesses and annealing process can be used to form both the p electrode490 and the p bond pad 495. The p electrode 490 and the p-bond pad 495can be formed using the same materials, such as, for example, a layeredmetal combination of Ni/Au.

In various embodiments, the disclosed layered structure in FIGS. 1-4 canbe used in the application of, for example, LEDs and/or lasers. FIG. 5depicts an exemplary semiconductor laser device 500 including asubstrate 505, a laser cavity 510 and a laser active structure 520. Thelaser active structure 520 can be configured within the laser cavity510, which can be configured over the substrate 505.

The substrate 505 can be any III-V compound semiconductor substrate,such as, for example, GaAs, InP or other similar material.

The laser cavity 510 shown is a cross-section for a lateral lasercavity, which can be used in, for example, edge emitting lasers. Inother embodiments, the laser cavity 510 can be a vertical laser cavityconfigured in, for example, vertical cavity emitting lasers. The lasercavity 510 can be oriented to provide an optical cavity mode for thesemiconductor laser device 500. In various embodiments, the length oflaser cavity 510 can be 100 microns or more. In various embodiments, thelength of the laser cavity 510 can be several hundred microns long.

The laser active structure 520 can be a layered structure similar to thedevices described in FIGS. 1-4 including a substrate 110, a buffer layer120, a first doped layer 130, a MQW structure 150, a second doped layer160, and a third doped layer 170. Likewise, a nanoscale strain array canbe included in the laser active structure 520 and disposed within atleast one of the first doped layer 130, the second doped layer 160 andthe third doped layer 170. In addition, laser facets, e.g., with highreflection, can be formed (e.g., coated) on the sides of the laseractive structure 520 for laser operations known to one of ordinary skillin the art.

The laser active structure 520 can be configured within the laser cavity510, for example, in a manner to provide a small periodic gain andrefractive index variation along the laser cavity 510 by turning thenanoscale strain array to a standing wave period in the laser activestructure 520. This can potentially be used to fix the phase of thestanding wave within the laser cavity 510.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A semiconductor device comprising: a substrate; a first doped layerover the substrate, wherein the first doped layer comprises a firstconductivity type; a multiple quantum well (MQW( structure over thefirst doped layer; a second doped layer over the MQW structure, whereinthe second doped layer comprises a second conductivity type opposite tothe first conductivity type; a third doped layer comprising the secondconductivity type formed over the second doped layer; and a nanoscalestrain array disposed within at least one of the first doped layer, thesecond doped layer and the third doped layer.
 2. The semiconductordevice of claim 1, further comprising a buffer layer disposed betweenthe substrate and the first doped layer, wherein the buffer layercomprises a nanoscale heteroepitaxy (NHE) buffer layer.
 3. Thesemiconductor device of claim 1, wherein the nanoscale strain arraycomprises a nanopatterned array with at least one dimension of about 100nm or less.
 4. The semiconductor device of claim 3, wherein the at leastone dimension of the nanopatterned array is about 20 nm or less.
 5. Thesemiconductor device of claim 1, wherein the nanoscale strain arraycomprises a nanopatterned array of steps and spaces.
 6. Thesemiconductor device of claim 5, wherein a period of the nanopatternedarray is about 200 nm or less.
 7. The semiconductor device of claim 1,wherein the MQW structure comprises a plurality of ordered In-richclusters.
 8. The semiconductor device of claim 7, wherein the pluralityof ordered In-rich clusters comprises a spatial layout of In-richclusters that extends from the at least one quantum well to a subsequentquantum well.
 9. The semiconductor device of claim 7, wherein each ofthe plurality of ordered In-rich clusters has a size of about 5 nm toabout 50 nm.
 10. The semiconductor device of claim 7, wherein each ofthe plurality of ordered In-rich clusters has a density of about 10¹⁰cm⁻² or more.
 11. The semiconductor device of claim 1, wherein the MQWstructure comprises at least one of InGaN and AlInGaN.
 12. Thesemiconductor device of claim 1, wherein each of the nanoscale strainarray, the first doped layer, the second doped layer and the third dopedlayer comprises one or more of GaN and AlGaN.
 13. The semiconductordevice of claim 1, further comprising one or more of light emittingdiodes (LEDs) and lasers.
 14. A method for making a semiconductor devicecomprising: forming a first doped layer having a first conductivity typeover a semiconductor substrate; forming a nanoscale strain array havingthe first conductivity type within the first doped layer; forming amultiple quantum well (MQW) structure over the first doped layer;forming a second doped layer having a second conductivity type over theMQW structure; and forming a third doped layer having the secondconductivity type over the second doped layer.
 15. The method of claim14, further comprising forming a nanoscale heteroepitaxy (NHE) bufferlayer between the first doped layer and the semiconductor substrate. 16.The method of claim 147, wherein the nanoscale strain array is formed byone or more of nanoimprinting lithography, interferometric lithography,immersion interferometric lithography, and nonlinear interferometriclithography.
 17. The method of claim 14, wherein forming the nanoscalestrain array comprises forming an array of steps and spaces.
 18. Themethod of claim 14, wherein forming the multiple quantum well (MQW)structure over the first doped layer comprises forming a plurality ofordered In-rich clusters.
 19. The method of claim 14, wherein thesemiconductor device further comprises one or more of light emittingdiodes (LEDs) and lasers.
 20. A semiconductor laser device comprising: alaser cavity; and a laser active structure disposed within the lasercavity, wherein the laser active structure comprises the semiconductordevice of claim
 1. 21. The semiconductor laser device of claim 20,wherein the nanoscale strain array in the semiconductor device of claim1 is tuned to a standing wave period.
 22. The semiconductor laser deviceof claim 20, wherein a length of the laser cavity is greater than 100microns.
 23. A semiconductor device comprising: an n-type GaN layer overa semiconductor substrate, wherein a nanoscale heteroepitaxy (NHE)buffer layer is disposed between the n-type GaN layer and thesemiconductor substrate; a nanoscale strain array comprising at leastone of GaN or AlGaN disposed within the n-type GaN layer, wherein thestrain array generates a periodic strain field; a multiple quantum well(MQW) structure comprising at least one of InGaN or AlInGaN over then-type GaN layer and overlapped with the periodic strain field; a p-typeAlGaN layer over the MQW structure; and a p-type GaN layer over thep-type AlGaN layer.